《2025年高中同步单元滚动强化卷高中英语必修第二册北师大版》

第二节(共 5 小题;每小题 2.5 分,满分 12.5 分)
阅读下面短文,从短文后的选项中选出可以填入空白处的最佳选项。选项中有两项为多余选项。
Freshwater mussels (贻贝) are critical to their larger ecosystems and the world around them. They create habitat for other species, like freshwater coral reefs, and help maintain the structure and rigidity (硬度) of the waterways they call home. _36_ Nearly three quarters of North America's roughly 300 native mussel species are endangered, at risk, or of danger. Dozens are already extinct.
_37_ For decades, freshwater mussels were over harvested for their shells. Before the age of plastic, they were collected and grown by the millions to satisfy commercial demand for buttons. Even more damaging was the spread of human development and environmental degradation (恶化). Rivers were dammed for power. Streams were diverted (使绕道) for agriculture. _38_ All this continues today, endangering far more than freshwater mussels. A recent report by the United Nations found that human practices have put roughly 1 million species at risk of extinction, many within decades.
The species-specific nature of the die-off suggests another cause: disease. The scientists have found a novel virus and a bacterium that are "statistically associated" with the dying mussels compared with control groups, but nobody is willing yet to identify which is the cause. _39_
Are the mussels dying because they're filled with virus and bacteria? Or are they full of virus and bacteria because they're dying? _40_ There are a million things it could be!
Nature is so complex. Biology is so complex. We do not understand how important some things are until they're gone.
A. Humans are the primary cause.
B. Wetlands were paved for housing.
C. There's still too much uncertainty.
D. Are there any more causes besides over harvesting?
E. But they are one of most endangered species on the planet.
F. On the other hand, they are the most important species in the ecosystem.
G. Is there an environmental cause driving it, such as drought or climate change?

答案： 语篇解读:本文是一篇议论文。文章主要讨论了淡水贻贝濒临灭绝的两个主要原因,其中最主要的是人为因素,其次是疾病。
36.E 后文提到大量贻贝濒临灭绝,处于危险中,有很多已经灭绝,故E项“但是,它们是地球上最濒临灭绝的物种之一”可以引起下文,符合语境。
37.A 后文提到淡水贻贝被过度捕捞,故A项“人类是主要原因”可以引起下文,符合语境。
38.B 上文提到人们为了发电而在河上筑坝,为了农业而使溪流绕道,故B项“湿地被填平用来造房”可以承接上文,都是人类破坏自然的活动,符合语境。
39.C 上文提到科学家已经发现了一种和濒死的贻贝有关的新病毒,但没有人愿意去确认导致贻贝濒临灭亡的具体原因,故C项“仍然有很多不确定性”可以承接上文,符合语境。
40.G 根据上文提到的两个问题及空后一句可知,G项“是否有诸如干旱或气候变化等环境因素在驱动它”承接上文,都是对贻贝濒临灭绝的原因的猜测,符合语境。